Two-way air cleaner for air compressors



Jan. 1, 1946. F. A. DONALDSON ET AL 2,391,837

TWO-WAY AIR CLEANER FOR AIR COMPRESSORS I Filed March 1, 1945' 5 Sheets-She't l OIL LEI/EL John 61 Enblom 19422) A. Donaldson Jan. 1, 1946. F. A. DONALDSON ETAL 2,391,887

TWO-WAY AIR CLEANER FOR AIR COMPRESSORS Filed March 1, 1943 3 Sheets-Sheet 2 Han/K A Donaldson 1707222 CI Eflblam 5% 27/ v? A770,? KS

Jan. 1, 1946. F. A. DONALDSON ET AL 2,391,887

TWO-WAY AIR CLEANER FOR AIR COMPRESSORS Filed March 1, 1945 3 Sheets-Sheet 5 m w m Patented Jan. 1, 1946 TWO-WAY AIR CLEANER COMPRESSORS FOB AIR Frank A. Donaldson and John C. Enblom,

St. Paul, Minn.

Application March 1, 1943, Serial N0. 477,550

8Claims.

Our invention relates to air cleaners of the ty which contain a body of free flowing liquid, usually oil, and which are commonly referred to in the trade as "oil washed air cleaners. Air cleaners of this general character are most commonly used in connection with internal combustion engines for cleaning the air delivered to the air intakes thereof and are generally preferred over other types of cleaners because of their relatively very high emciency, their low restriction to air flow and because they require a minimum of servicing. However, oil washed air cleaners such as were hitherto used in connection with internal combustion engines have not been satisfactory for use in connection with air compressors of the continuously operated variety for the following reasons, to wit: Air compressors of this type are usually operated continuously to maintain a pre-determined pressure in a storage tank and when the pressure in the tank reaches the pre-determined point, the practice is to hold the compressors intake valve open so as to render the compressor inoperative to further compress air without stopping the compressor. Otherwise stated, compressors or pumps of this type are operated continuously even when the demand therefor is intermittent, are permitted to function normally during intermittent ,work demand periods, and are idledv with their intake valves open between intermittent work periods. When the compressors intake valve is thus opened, air is alternately sucked into the engine's intake by the compressor piston and then discharged from the compressors intake by the compressors piston so that the compressor merely breathes the same amount of air in and out through its intake. Now "oil washed air cleaners of the conventional variety used in connection with internal combustion engines are capable of handling air moving therethrough in one direction only and will lose their liquid through their intakes under high velocity movement of air therethrough in a reverse direction.

The advantages of using the "oil washed type of air cleaner in connection with such compressors has long been recognized, but the development of air cleaners of this type which would operate successfully in connection with such compressors where the air cleaner is subject to a two-way movement of air a large part of the time has proven very diiiicult of solution. Probably the most successful attempt to solve this problem hitherto has been to provide for the automatic relief of air pressure, in what normally constitutes the outlet portion of the cleaner, under reverse fiow of air through the cleaners outlet so that the backwardly directed air would be permitted to escape to atmosphere without passing through the liquid sump portion of the cleaner and the cleaners intake. However. this prior scheme involves the use of reliefvalve mechanism which is the constant source of trouble and will most inevitably leak and upset the efllciency of the cleaner during normal operation. Our invention provides a simple and inexpensive yet high eflicient air cleaner of the so-called oil washed variety which will operate with complete satisfaction when connected to the air intake of a compressor of the type described, will thoroughly clean the air delivered to the compressor under both normal operating conditions and during periods that the compressors intake valve is held open, and will thoroughly remove the liquid from the air under either direction of movement of ai through the cleaner and this without the use of relief valves or other moving parts. Another important objective of the invention is the provision of a simple and inexpensive device which can be readily attached to oil washed cleaners of the variety commercially used in connection with internal combustion engines to convert the same intoa two-way air cleaner for use in connection with continuously operating air compressors.

The above and other highly important objects and advantages of the invention will be made apparent from the following specification, claims and appended drawings.

In the accompanying drawings wherein three forms of the invention are illustrated:

Fig- 1 is a view in vertical, axial section showing one form of the invention applied to an air cleaner oi the character fully disclosed in the prior patent to Wilfred W. Lowther No. 2,000,706 of May 7, 1935:

ing another form of the invention applied to the intake end of a similar air cleaner structure but which is more nearly represented in the prior Lowther Patent No. 2,069,889 of February 9, 1937; and

Fig. 3 is a view in vertical, axial section showing still another form of the invention applied to a cleaner of the character fully disclosed in the Lowther prior art Patent 2,130,142.

With reference now to Fig. 1, the conventional parts of the cleaner will first be described.

The casing or shell of this cleaner of Fig. 1 is preferably cylindrical in form and comprises a main cylindrical section 3 that is permanently closed at its upper end by a head 4 and which is primarily open at its lower end but is normally closed at its lower end by a liquid sump-forming cup 5 that is telescoped over the lower end portion of the casing section 3. This sump-forming cup 5 is slid on to the lower end of the section 8 to the full extent permitted by engagement of the upper end of said cup with a head 8 and is detachably held in place by spring pressed clamps 1. The oil cup 5 may be assumed to be filled Fig. 2 is a view in vertical, axial section showwith oil to the level of a bead I. and the broken line marked "oil level.

Opening through the closed top of the cleaner and extending axially downwardly through the cylindrical cleaner casing to a level preferably below the oil level is an axial air intake tube or conduit 9 having at its lower delivery end a radially projecting annular flow restricting flange or bailie l0. Rigidly mounted on the bottom of the sump-forming cup in axially spaced relation thereto is an annular baflle II, the upper portion of which extends somewhat above the delivery end of the intake tube 9 and the oil level. This annular baille II is concentrically disposed with respect to the casing and intake tube 9 and is spaced from the periphery of the bafl'ie flange II to afford an annular air passage l2 therebetween and the intake tube 9. The baffle ll. while described as being open. at its bottom and spaced from the bottom of the oil sump 5, may also be in the nature of a closed bottom inner oil cup of the nature shown in Patent No. 2,069,889, above more fully identified.

That portion of the interior of the cleaner casing surrounding the air intake tube 9 above the oil level constitutes an enlarged annular passage or expansion chamber which is preferably filled with an air pervious liquid intercepting and collecting element at least to the level of the cleaners outlet passage or port I3, which port opens through the upper extremity of the cylindrical wall of the casing and is extended by means of a tubular coupling sleeve I that is adapted to be connected to a compressors intake conduit. The intercepting and collecting element just referred to is preferably of the type disclosed in the prior art Schulz Patent No. 2,011,303 of August 13, 1935, comprising stacked corrugated screens 15 of the woven wire variety. The function of the screens l 5 is to collect and return liquid to the sump and to aid in air cleaning action.

Under normal operation of the cleaner, air will flow through the cleaner in one direction only, coming in through the intake tube 9, discharging downwardly into the liquid sump, reversing its direction of travel within the bailie I I, passing upwardly through the annular air passage l2 into the expansion chamber, passing upwardly through the screen filled expansion chamber and out the outlet port l3 to the intake of the compressor. During this normal function of the cleaner, a considerable amount of sump liquid is carried upwardly into the screen filled expansion chamber with the air entering the same, but this oil or other liquid is intercepted by the screens I5 and drained back to the liquid sump so that the air passing out of the outlet port I3 is in a substantially dry condition.

Obviously, as thus far described, the cleaner is only a one-way acting device, there being no means provided for intercepting oil carried into the cleaners intake duct 9 under reverse or backward travel of air and delivering such intercepted 011 back to the liquid sump.

In accordance with the present invention, we provide on both sides of the liquid containing sump of the cleaner means for intercepting liquid and returning the same to the liquid sump so that the cleaner will function with substantially identical efliciency and safety against oil loss under either forward or backward travel of air through the cleaner. In the form of the invention shown in Fig. 1, this important result is accomplished by the simple expedient of placing in the cleaners intake conduit 9 a suitable air perarenas:

vious liquid intercepting and collecting element which, as previously described, comprises a superimposed plurality of corrugated woven wire screens l5. Preferably, and as illustrated in Fig. 1, the intercepting element made up of the superimposed corrugated screens I5 is contained within a tubular retainer I that functions as an auxiliary air intake tube and is telescopically ap plied through the upper end of the intake tube I to the maximum extent permitted by engagements of the stop bead I with the top I of the casing. This tubular retainer 8' is slidably removable through the intake t-ube 8 and is normally held in place only by gravity and friction. The stacked screens ii are locked in place within the tubular retainer 9' by inwardly projecting upper and lower annular flanges i! on aid tube 9'. The screens l5 may be assumed to be made of the same kind of woven wire as are the screens l5, but in this case the corrugations are parallel and extend each completely across the circular screen, the corrugations of alternate screens being angularly disposed to prevent nesting. Because of the restriction to air new set up by the screens IS, the cross-sectional area of the intake tubes 9 and 9' should be increased somewhat over what would be necessary in a cleaner devoid of such screens in the intake end thereof and so that the minimum open area cross-sectionally thereof will at least equal that of the outlet port I3.

Under normal operating conditions of a compressor to which this cleaner is connected, the cleaner will function in the usual manner, air passing downwardly through the air intake tubes 9 and 9 and upwardly through the screenequipped expansion chamber surrounding the intake tube and out the intake port [3 to the compressor. However, when the intake valve of the continuously operating compressor is held open to prevent further charging of a storage tank, or the like, the air flow through the cleaner will be alternately inwardly and outwardly through the cleaner in high velocity pulls of air; this being especially true and especially serious in connection with single cylinder compressors, but being also serious in connection with multiple cylinder compressors. Under these conditions, of alternate inward and outward pulsation of air through the cleaner, oil displaced from the well into the annular expansion chamber surrounding intake tube 9 under inward pulsations of air through the cleaner, will be collected and extracted from the air stream by the screens I! before the air reaches the outlet port I 3 and during reverse pulsations, oil carried into the intake conduit or tube 9 with the outwardly traveling air will be collected and separated from the outwardly moving air by the screens IS in the intake tubes 9 and 9'. When air moving backwardly through the cleaner reaches the extreme upper end portion of the auxiliary air intake tube 9, the oil will have been completely extracted from the air so that the air will be discharged therefrom in a dry condition. The oil collected on the screens l5 and I5 will flow down the screens and drain back into the oil sump where it can be re-circulated.

In the arrangement described, the lower of the screens l5 will be thoroughly wetted with oil during the time that the intake valve of the compressor is open. although the upper of the said screens I5 will remain in a substantially dry condition at all times. Since the lower portion of the intercepting element, made up of screens man,

through the cleaner and will go a long ways toward increasing the over-all efllciency of the cleaner by collecting therein a considerable volume of dust. However, when the compressor is again operated with its intake valve open, the alternate outward pulsations of air through the cleaner will again carry a volume of liquid into the screens l6 and this liquid will tend to wash the screens and return the dirt picked up thereby back to the liquid sump and leaving the screens largely free of collected dirt preparatory to the next period of normal operation. screens IE will be largely cleaned by automatic action, it is, nevertheless, desirable that they be readily removed for cleaning since they may need servicing more frequently than the cleaners liquid sump. With the device shown in Fig. 1 this can be accomplished readily by merely withdrawing the auxiliary tube 9' and flushing the same out in gasoline or other solvent.

With reference now to the device shown in Fig. 2, it may be said that those parts of this cleaner which are old in the above identified Lowther Patent No. 2,069,889 are so closely analogous to the conventional or prior art parts oi the device of Fig. 1 that they will be indicated by characters like those assigned to corresponding parts in Fig. 1 plus the exponent a. In Fig. 2, therefore, the cylindrical shell of the casing is indicated by 311 and the closed upper end thereof, which in this instance is concave, is indicated by 4a. The casing 3a is primarily open but is normally closed by an oil sump-forming cup 5a that is telescoped on to the lower end of section n to the extent permitted by an annular bead 6a. In this Fig. 2 the oil is detachably held in lace by means of wing nut-equipped clamping latter is preferably composed of a plurality of superimposed corrugated screen sections 2| which may be assumed to be like the screens I! of Fig. 1. The screens 2| are held in place against downward movement in the shell section by an annular flange 22 and are held against upward displacement by an annular flange 22, said flange 23 being permanently secured to the upper end of shell section 2|. The inverted oil trapping cup 2i is welded or otherwise rigidly secured to the center of a spider 24 which has circumferentially spaced portions that span the am While the nular air passage between flange 23 and trapping element 2|. The spider 24 terminates in a peripheral annular flange 25 that is screw-connected to the flange 23. The lower edge oi. the shell section 20 is formed with an annular coupling flange 26 that seats on the rolled edge I! of shell section in and is flrmly but removably held in place by a cross-sectionally channel-shaped split clamping band 21.

bolts 1a. The normal static oil level of the cleaner .iecting annular flange of a closed bottom inner oil cu that is rigidly mounted on the bottom of the oil sump-forming element 5a. This cup II a is preferably provided with oil metering openings Hi. Since the normal action of this cleaner is substantially like the action of the cleaner of Fig. 1, no detailed description of. the operation of the device of Fig. 2 will be given. Of course. the cleaner of Fig. 2. as thus far described, is old in the art and while suitable for internal comst on use, is not suitable for constantly operating compressor use for reasons above pointed out in connection with Fig. l. I

In adapting the present invention t the cleaner of Fig. 2 we preferably detachably apply to the upper end of the casing section 342, which terminates in a bead IS, an auxiliary oil trapping and air cleaning device which will immediately be described. This auxiliary device for converting a conventional cleaner to a two-way air cleaner preferably, and as shown here n. compri es a or. lindrical outer shell 20, an inverted oil trapping cup 2| eo-axially aligned with but spaced fr m the cleaners intake tube 9a. and an annular liquid intercepting and collectin element, which Under normal operation the uni-directional air flow through the cleaner will be as shown by direction arrows in Fig. 2 which briefly described is as follows: The air will first pass downwardly through the screen-equipped annular chamber of the auxiliary device, downwardly through the air intake .tube 9' to the liquid sump, upwardly through the. screen-equipped expansion chamber surrounding the intake tube 9' and out through the clean air outlet port |3a to the compressor. Under this action, of course, the dust will be removed from the air by impingement in the liquid well and by subsequent trapping of the oil that is in the lower portion of the screen-equipped expansion chamber, and the oil will be removed from the air before it passes out the outlet port l3a. However, when the intake valve in the compressor is held open, the resultant pulsating inward and outward movement of air through the cleaner will cause oil to be discharged upwardly through the intake tube 911 at high velocity during each outward pulsation of air, and this outwardly discharged Oil will be largely blown directly into the inverted oil trapping cup 2| from which it will be permitted to flow back to the oil sump during the alternate incoming air cycle. However, some of the oil discharged outwardly through the intake conduit 9a during outward pulsations will be carried into the screen-equipped annular chamber surrounding the trap 2| in the auxiliary device and this oil will be intercepted and collected by the screens 2| only to be permitted to drain back during altemat inward pulsations. In this device, as in the previously described de-- vice, the oil carried into the annular chamber of the auxiliary device during outward air surges will be removed from the air before the air is discharged through the annular prlmary air intake passage 28 at the top of the auxiliary device. Also in this form of the invention, as in the previously described form, the intercepting element of the auxiliary device will serve as a primary air filter during normal cleaner operation and will be largely washed free of dirt during the next abnormal period of compressor operation when its intake valve is open, Also in this device, as in the previously described arrangement, the auxiliary device is quickly removable by merely removing or loosening the clamping band 21 for flushing out in gasoline or other solvent.

The air cleaner of Fig. 3 is, as previously indicated, of the same general construction as is shown in the prior Lowther Patent 2,130,142, and is comprised mainly as follows: The outer shell or casing of this cleaner is made up of an inverted cup-like upper section 33 and a lower cup-like section 3|. The upper section 33 includes a more or less dome-shaped head element 32 and a rigid- 1y anchored depending skirt 33; The cup-like lower section 3| provides a liquid sump 34 in its bottom, which is usually filled with oil to the level indicated on Fig. 3, and is expanded radially above the static oil level line and formed to provide an up-standing annular flange 32 that ielescopically receives the depending skirt 33 of the inverted cup-like upper section 33. Rlgidly anchored to the radially intermediate portion or the head element 32 is depending skirt flange 3i and a more or less radially extended baiiie plate 33 having a plurality of large circumferentially spaced air passages 31. At its central portion the baflie 33 is formed with an axial air passage defined by a more or less conical flange 33. Telescopically applied over the flange 33 and rigidly secured to and depending from the bafile 36 is a sleeve 38. This sleeve 33 may be assumed to be welded to the baiiie 33 at 40 and forms the inner annular wall of an expansion chamber 4| overlying the liquid sump or well, and the outer wall of which expansion chamber 4| is formed by the depending skirt 3!. The bottom of the cup-like lower section 3| is upwardly inclined toward the axis or the cleaner and is provided with a short annular anchoring flange 42 against which the lower edge of the depending sleeve 33 is normally seated. Extending through the anchoring flange 42 and largely through the depending sleeve 39 is a cleanv air discharge tube 43 that is rigidly anchored to the flange 42 by spot welding or the like as at 44.

This discharge tube 43 does, therefore, become a i unitary part or the cup-like element 3| and is removably irictionally engaged with the depending sleeve 39 and has its upper end projected under the lip of flange 33, which flange 33, together with the baiile 36, sleeve 33, and depending skirt 3!, is a unitary part or the inverted cup-like upper portion 30 of the cleaner. The upper and lower sections of the cleaner are normally but removably anchored together by means of a thumb-nut-equipped screw 45, the lower end of which screw 45 is rigidly anchored to a narrow anchoring bar 46 that extends across the interior of the upper portion of the air dischargetube 43 and is secured thereto at its ends by spot welding and the like. The clean air outlet tube 43 is adapted to receive the intake end of the air intake conduit (shown only by dotted lines in Fig. 3) or a compressor, and is equipped with a suitable clamping bar 41 and a sealing gasket containing a flange 48. As in the prior Lowther Patent 2,130,142, there is provided within the liquid sump of the cleaner an up-standing annular flange 49 having circumferentially spaced liquid passages I50, and the expansion chamber 4| is equipped with an air pervious liquid intercepting and collecting element which is preferably, and as illustrated, made up of a plurality of stacked corrugated annular screens 5i, which have the same purpose and function as do the screens i5 and I! of Figs. 1 and 2 respectively, which is that 01' collecting and returning liquid to the sump before it reaches the cleaner outlet under normal cleaner operation.

The depending skirt 33 of the inverted cup-like upper section of the cleaner is provided near its top and above the flange 32 with a circumferentially spaced plurality of air intake ports 52 which lead into an annular downwardly directed air intake passage 53 from which air is normally discharged downwardly into the liquidsump from accuse-r which the air passes upwardly into and through the expansion chamber 4i, irom which it normal- 1y passes outwardl through the air passages 31 and outlet. tube 43. However, when the intake valve 01' a continuously operated compressor is held open to prevent further charging of the storage tank, or the like, and the resultant air flow 52 under the conditions noted is largely or entirely eliminated by interposing in said passage 33 a suitable air pervious liquid-collecting and returning element which, as shown and preferably, is in the nature oi. stacked corrugated screens 34, which serve in the same capacity as do the screens 2| of Figs. 1 and 2 respectively, and which is to collect and return liquid to the liquid sump.

In carrying out the invention hereof, it is important that the intercepting means or elements or the inlet and outlet passages of the several forms of cleaner be in drainage communication with the liquid sump, and also that said means provide a i'oraminous mass which completely fills the respective air passage for a substantial depth so as to accomplish the assigned function, which is to intercept, and drain back to the liquid sump such liquid as may be carried thereinto from the sump under rapidly reversing air flow conditions such as are produced in the intake of a compressor by holding open its intake valve.

Throughout the specification wherever the elements l5, l5, It, 2|,ll and I4 rei'erto ascreen,

it will be understood to mean any known or approved pile of air pervious dust and liquid intercepting and collecting means as used in air cleaners of the general character herein shown and described.

What we claim is:

1. In a two-way air cleaner of the liquid washed type, a main vertically disposed cylindrical casing providing a liquid sump in its bottom and having a closed top, an axial air inlet tube up. wardly opening through the closed top of said main casing section and downwardly discharging into the liquid sump, said axial inlet tube defining with said main casing an annular expansion chamber above that portion of the liquid sump radially outwardly or said tube, a pile of air pervious dust and liquid intercepting and collecting means filling a substantial portion of said expansion chamber, an outlet leading from the upper portion of said expansion chamber and adapted to be connected to the intake of an air compressor, an auxiliary liquid trapping and collecting device applied to the top of the main cleaner casing and comprising a cylindrical shell d tachably applied to the upper peripheral portion of the main cleaner casing and being open at both ends for passage 01' air to and from said axial section and through which air must pass on its way to and from the cleaners axial air inlet tube.

2. In a two-way air cleaner of the liquid washed type, a main vertically disposed cylindrical casing providing a liquid sump in its bottom and having a closed top,'.an axial air inlet tube upwardly opening throughv the closed'top of said main casing section, said axial inlet tube pansion chamber above that portion of the liquid sump radially outwardly of said tube, the'lower end of said tube and expansion chamber drain ing into the sump and being so close to the sump that air passing .from either thereof to the other thereof will pass through the sump and .-carry liquid therewith into the other'thereof, a pile of air pervlous dust and liquidinter'cepting and collecting means filling a substantialp rtion of said expansion chamber, an outlet leading from the upper portion of said expansion chamber and adapted to be connected to'the intake of an air compressor, an auxiliary liquid trapping and-collecting device applied to the top of the main? cleaner casing and comprising a cylindrical shell detachably applied to the upper peripheral por-i; tion of the main cleaner casing and being open] at both ends for passage of air to and from saidv axial air inlet tube, an invertedlliquid trapping defining with said main casing an annular exnular air passage surrounding said axial tube,

said passages extending upwardly from and being in drainage communication with the sump,

the lower ends of said passages being so closely associated with the sump that air passing from either thereof to the other thereof will pass through the sump and carry sump liquid into the other passage, the upper portion of the annular :air passage being adapted for connection to the intake or anjtair compressor, and air pervious liquid intercepting means completely filling each of said passages tor a substantial depth'so'as to intercept and drain back to the liquid sumpsuch liquid as may be-carried thereinto from the sump.

: 5. The structure defined in claim 4-in.'which the said intercepting and collecting means of the said axial air passage is contained within atubular retainer that is telescopically applied within I the axial air tube and is upwardly displaceable .irom said axial air tube.

cupdisposed in the auxiliary section in co-axial' alignment with the upper end voi! said .air inlet tube, the said inverted liquid trappingcup having an open lower end of a diameter at least equal to that of the upper end of the axial air intake tube and forming with said auxiliary shell section an annular'air passage, and an air pervlous liquid intercepting and collecting element fillin a substantial portion 'of the said annular air passage of the auxiliary casing section, the last said liquid intercepting and collecting element being in drainage communication with the liquid sump through said axial air inlet tube and being of sufiicient depth and density to intercept, collect, and drain back to the liquid sump such liquid as may be carried thereinto from the sump.

3. In an air cleaner for use in connection with the intake of an air compressor of the continuously operating type wherein air fiow through its intake is unidirectional during work periods and is repeatedly reversed during idling periods, a casing providing a liquid sump in its bottom, wall structure providing two upwardly directed air passages having open lower ends in drainage communication with the sump and located so tube defining with said main casing an annular 85 6. In a two-way air cleaner of the liquid washed type, a main vertically disposed cylindrical casing/providing a liquid sump in its bottom and having a closed top, an axial air inlet tube upwardly opening through the closed top of said'main casing section and downwardly discharging into the liquid sump, said axial inlet expansion chamber above and in drainage communicationzwith that portion of the liquid sump radially outwardly of said inlet tube, the lower end of said'tube and said expansion chamber being'so close to'the sump that air passing from either thereof to the other thereof will pass through the sump and carry liquid therewith into the other thereof, a pile of air pervlous dust and liquid intercepting and collecting means filling a substantial portion of said expansion chamher, an outlet leading from the upper portion of applied to the top of the main cleaner casing and comprising a cylindrical shell detachably applied to the upper peripheral portion of the main cleaner casing and being open at both ends for passage of. air to and from the said axial air close to the sump that air passing irom the lower end of either of said passages to the other thereof will pass through the sump and carry liquid therefrom into the other passage,-the upper end or one of said passages being in communication with atmosphere and the upper end ofthe other thereof. being adapted for connection to the intake or an air compressor, an air pervlous liquid intercepting mass completely filling one or said passages for a substantial depth whereby to intercept, collect, and drain back to the sump such liquid as may be carried thereinto under continuous movement 0! air upwardly therethrough,

and a similar air pervlous liquid intercepting mass completely filling the other of said passages for a. substantial depth so as to also intercept, collect, and drain back to the sump such liquid as iscarried upwardly thereinto under conditions or rapid reversing or air flow therethroush.

4. In an air cleaner-oi the liquid washed type, a' vertically disposed casing having aclosed top inlet tube, the air passage through said auxiliary casing section being in drainage communication withsaid sump through said axialinlet tube,

and an air pervious liquid intercepting and collecting means filling a substantial portion of the 1 air passage through saidauxiliary casing section andlbeing of sufiicient depth and density to intercept, collect, and drain back-to the liquid sump. such liquid as may be carried thereinto from the sump.

. ers of woven wire screen.

8. The structure defined in claim 3, in which the said intercepting and collecting .mass or each oisaidpassages comprises a multiplicity of adjacent layers of woven wire screen.

FRANKA. DONAIiDSON. JOHN C. ENBLOM.

7. The 'structure'defined in claim 2, in which i 

